Unless it's too late:

sunbird-1.0-0.3.20090302hg.fc11
* Fixes an issue where the migration dialog showed up after first launch of thunderbird is invisibly small [https://bugzilla.redhat.com/show_bug.cgi?id=499346]
* Given the dialog is modal, the thunderbird becomes practically unusable, which is s pretty bad ftue
* Tiny two-liner patch, which just adds the dimensions instead of relying on default, already upstream
* An update will probably happen later in F11 lifecycle once stable sunbird 1.0 is released
* Sunbird is a quite big package, saving users from having to do a 0day update is certainly an advantage